Published online Feb 7, 2020. doi: 10.3748/wjg.v26.i5.499
Peer-review started: November 5, 2019
First decision: December 7, 2019
Revised: December 13, 2019
Accepted: January 2, 2020
Article in press: January 3, 2020
Published online: February 7, 2020
Gastric cancer (GC) is one of the most common types of cancer. The detailed roles of miR-34c and E2F transcription factor 1 (E2F1) have been proven in various cancer types. However, the relationship between them and GC has not been understood.
The promoter region of miR-34c was predicted to have a binding site in E2F1 by PROMO database. E2F1 was increased but miR-34c was decreased in GC. The relationship between them in GC has not been understood. Thus, it is required to study the function of E2F1/miR-34c in GC.
To investigate the effect of miR-34c and its upstream transcription factor E2F1 on paclitaxel combined with cisplatin resistance in GC cells.
Paired GC tissues and adjacent normal tissues were randomly sampled from 74 GC patients. MiR-34c and E2F1 were detected by qPCR and Western blot. In addition, the drug resistance of GC cells to paclitaxel and cisplatin was induced by the concentration gradient increasing method, and changes in miR-34c and E2F1 during this process were detected. Furthermore, E2F1 and miR-34c overexpression or low expression vectors were constructed and transfected into drug resistant GC cells. Moreover, MTT was employed to detect the sensitivity of cells to paclitaxel combined with cisplatin, qPCR was adopted to detect the expression of miR-34c, Western blot was applied to detect the expression of E2F1, drug resistance-related protein and apoptosis-related protein, and flow cytometry was used to detect cell apoptosis and cell cycle status.
E2F1 was overexpressed while miR-34c was underexpressed in GC. After inducing GC cells to be resistant to paclitaxel and cisplatin, E2F1 expression increased while miR-34c expression decreased. Both silencing E2F1 and over-expressing miR-34c could increase the sensitivity of drug-resistant GC cells to paclitaxel combined with cisplatin, promote cell apoptosis and inhibit cell proliferation. Among which, silencing E2F1 could reduce the expression of drug resistance-related proteins and apoptosis-related proteins, while over-expression of miR-34c could upregulate the expression of apoptosis-related proteins without affecting the expression of MDR-1, MRP and other drug resistance-related proteins. Rescue experiments demonstrated that inhibiting miR-34c could significantly weaken the sensitization of drug resistant cells and Si E2F1 to paclitaxel combined with cisplatin.
E2F1 inhibits miR-34c to promote the proliferation of GC cells and enhance the resistance to paclitaxel combined with cisplatin, while silencing E2F1 is conducive to improving the efficacy of paclitaxel combined with cisplatin in GC cells.
Slicing E2F1 or increasing miR-34c improves the sensitivity of GC cells to paclitaxel combined with cisplatin, and enhances the therapeutic effect of drugs. To advance research on the effect of E2F1/miR-34c on GC cell resistance, further discussion will be conducted in future studies: (1) Whether E2F1 directly targeting regulates MRP and MDR-1; (2) Which downstream target genes are implicated in the regulation of E2F1/miR-34c on the proliferation and apoptosis of GC cells; and (3) The relationship between miR-34c and the drug resistance of GC cells, which all require further study.